In 1990, Sue Hendrickson discovered the largest and most complete T. rex fossil ever found. Named after her, ‘Sue’ is on display in The Field Museum, Chicago.

What was so important about your discovery?
First of all, she was so complete. There had been eleven previous T. rex discovered but the most complete any of them had been was around 50 per cent. Sue is considered to be 90 per cent complete. That level of completeness is scientifically very important as we have learnt so much from her.

Once she had been prepared and studied there were no longer any questions about T.rex dimensions. We could carry out CT scans of her skull to figure out how large her brain was and how it functioned.

Then there’s the fact that her bone quality is just awesome. It’s like what you dream about when you’re out in the field looking for bones. Usually you uncover quarter of an inch and then pour in glue so the bones don’t fall apart or turn to powder. I picked up some of her bones with no glue at all. That’s unheard of.

Finally, Sue’s important because she is a she. When we found her, even though the guys named them after me (which I wish they hadn’t) we didn’t know she was female. Now we do. The Field Museum won’t commit to this because they’re overly cautious but many paleontologists agree that the largest T. rex found up to now is a female.

Let’s go back to 1990 and Sue’s discovery. You were working with a team from Black Hills Institute of Geological Research in South Dakota. Did you head out there to find a Tyrannosaurus Rex?
Not at all. We’d were working at the Black Hills Institute quarry and had a couple of weeks to spare as we were waiting for a film crew to turn up. There were only three of us left there, so we started to scout the neighbouring ranches and found pretty good things including three Triceratops skulls, the best of which was around 30 per cent complete, which is good for a Triceratops.

One morning I noticed an area that we hadn’t spotted before and thought I should head out there. For one reason or another, I never had the time. Then, the day before we were due to leave, we had a flat tyre on our van and the spare was quite low. I told the guys that if they were heading into town to get it fixed, I’d go and check out that place I’d been meaning to.

It was a five or six mile hike and as soon as I got there, I started walking along the cliffs looking for bone fragments. I found a few and looked up the hill to see bones sticking out about eight feet up.

What did you find?
When I climbed up, I saw that there were three articulated vertebrates, some ribs and part of a pelvis, although I didn’t know what that was at this point. Ribs and invertebrates are easy to identify, pelvises are harder.

I was quite excited that the vertebrates were still articulated, as that usually means there’s a good chance there’s more.

Did you immediately recognise them as Tyrannosaurus Rex bones?
They were going into the hill at both ends but I could tell that it was a carnivore as their vertebrae are hollow and quite a different shape. Of course, at that time the only large carnivore was T. rex. It took me a few minutes to absorb what I’d found.

Did you immediately share what you’d found?
It took me a couple of hours to walk back to where the guys were working on the Triceratops. I’d brought back some scraps of bones because I knew they’d never believe me if I told them I’d found a T. rex.

Immediately, we all jumped in the truck and drove as close as we could so I could show them. Now Pete [Larson, the leader of the expedition] was the screamer of the group and he was jumping up and down and yelling, “It’s all there.” But of course we didn’t know that was true until we started work on getting her out.

How long did the excavation take?
I suspect it was a world record for the fastest excavation ever – around 17 days. We waited a couple of days because Pete wanted his brother to come over to help – he didn’t tell him why until he arrived.

The first five days were the worst because we had to work through 30 feet of rock in temperatures around 130 degrees. But, once we got down to the bones we saw she was still mostly articulated, so it meant we wouldn’t have to excavate a huge area. Most bones are scattered and can be over a half-mile area but these were all together.

Her legs were slightly disarticulated but right next to her and we couldn’t find the skull at first. It was the last thing we found, tucked under the pelvis. It took two years to get her skull apart from the pelvis.

When you saw Sue in her entirety could you believe what you’d found?
I was in total disbelief. It’s still hard to believe now. Finding Sue was like winning the lottery a million times over. I suppose the odds are stacked against such a discovery. Think of a herd of cows out on the plain. A few die but only the one cow that falls into the river and gets rapidly covered in mud or sand is going to be preserved.

Years later, when you’re looking for its remains, you’re searching in an area of a thousand square miles. You need to walk past at the exact point when the bones are eroding out.

Usually you only find fossils when the last bones are eroding. These were the first. In all the years I’d been hunting for bones, the only T. rex remains I’d ever found was some shed teeth. I’d never found even a scrap of bones. And before Sue, if you uncovered just two T. rex bones, it was considered a good find.

After the excavation, things didn’t go to plan. Even though your team had paid the farmer who owned the land a discovery fee, there was a legal tussle over custody of Sue wasn’t there?
It was very, very ugly. From the most wonderful time of my life, it became the most devastating time. The FBI got involved and the US Attorney. Fortunately, the US Attorney eventually realised that there was no wrongdoing. Permissions to excavate had been sourced. Black Hill was very careful about that kind of thing.

In the end, Sue was put up for auction and was won by the Field Museum of Natural History in Chicago for $8.36 million. A lot of weird things happened to Sue. That fact that a dinosaur was even auctioned at Sotheby’s in New York for one, and then, to top it all, McDonalds and Disney put up most of the money. They said that they purchased Sue as a gift to the world’s children in the hope that she would inspire education. I couldn’t think of a better use for her.

Do you still visit Sue?
I did when she was first unveiled but not so much now. It’s weird. I honestly don’t think I should have been the one to find her. I’m a very quiet person, happiest when I’m out in the field or diving looking for stuff.

I know a lot of people who’ve dedicated their entire life into searching for dinosaurs. I’ve put a lot of hard work into it too, but it’s too bad that one of them didn’t find it. I know people like the fact that a woman found her and we need women role models, but it should have been a 20-year-old female paleontologist who could have made a full career out of her. I was 40 when I found Sue and didn’t need any more doors opened. I was already doing what I loved.

About five ago I stopped saying yes to things connected to her, because I didn’t want to feel guilty anymore and don’t see her too often. She’s not mine. While morally I’ll always consider her belonging to the Black Hill Institute, I’m glad she’s at The Field Museum. She has a lot of impact on a lot of people. That’s a good thing.

Sue Hendrickson was speaking to Cavan Scott